Terra Nova Jupiter

Lightest hooped bivi: Outdoor Research Helium Bivy

At only 510 grams (18oz), this is the lightest hooped bivvy bag by a long stretch. It also happens to be much cheaper than most others. It is less than half the price of the Terra Nova Jupiter.

I’ve been using one for a couple of years now and reckon it’s excellent. It is not as sturdy as the heavier Terra Nova Jupiter so will no doubt be more susceptible to wear and tear. But, all in all, it is a really good bag for the price, especially given how light it is.

Rab Survival Zone bivvy

BIVVY BAG BUYER’S GUIDE

This should help inform your purchase so you know what to look for in a good bivi.

Waterproofness

Waterproofing is measured with a rating called hydrostatic head (HH). 10,000 or more means you’ll stay dry in all but the worst weather. Lower than that and it will probably start to seep through in heavy weather and puddles. I have a bag with a rating of 1,000 which is fine for spills and brief showers but lets water through in anything more.

Any bivvy bag made with Goretex or eVent will be waterproof.

Breathability

Breathability is the extent to which the fabric will allow water vapour to escape. It is particularly important in bivvy bags because, unlike tents, any condensation that forms inside them will instantly make you and your sleeping bag feel damp.

If the bivvy bag you are interested in uses Goretex, eVent or Pertex then its breathability will be fine. Don’t give it another thought.

If it is not made with one of those branded fabrics, then look at its MVTR: moisture vapour transmission rate. That is a measure of its breathability. 10,000 or more is fine. Goretex and eVent should be 25,000+. Less than 10,000 becomes damp and sweaty.

If a bivi bag is cheap then it is very likely that it will either be not very waterproof or not very breathable. A bit of reading between the lines will usually tell you which.

Hooped or not hooped

Basic bivvy bags are just large, waterproof bags. They are cheap, lightweight and instant to pitch but can be miserable in wet weather.

Hooped bivvy bags are like tiny tents. They are more expensive and take a couple of minutes to pitch but they are much better in the rain.

Entry and exit

Non-hooped bags may have velcro, zips or draw-cords at the top closure where you get into and out of the bag. This is a matter of preference though I would probably opt for the simplicity of drawcords.

Packed size/weight

Bivvy bags are generally fairly lightweight. The lightest one weighs just 200g.

However, some of the fancier hooped bivvies can weigh over a kilogram and ex-army bags are often 800g. Given that you can get one-person tents that weigh less than a kilo these days, it is worth paying some attention to the weight.

Weights of all bags are displayed in the tables below.

Cost

Prices range about £30 for a budget ex-army bag to a whopping great £350 for the luxurious Terra Nova Saturn. If price is an issue, you can always just get an orange survival bag for £4 and make do with that.

–

Buying online?

If you decide to buy a bivvy bag after reading this article, please do consider using one of my links.

If you do, at no cost to you, I will get a small percentage of whatever you buy.

All hooped bivvies have mosquito nets.

To sort table by weight, use the ‘Ounces’ column. It works better.

REVIEWS

a. Basic bivvy bags

Your basic non-hooped bivvy bag is just a big waterproof sack that you get inside. Their beauty is their simplicity: no poles, no pitching and, usually, no zips. Their biggest downside is that they’re a pain in the rain: the best you can do is to flap a hood over your face and breathe Goretex until it passes. Here is an overview of the most common types of bivvy sack and the best:

Available for less than £5, the orange emergency survival bag is lightweight, 100% waterproof and a viable option in some circumstances (e.g. if it’s breezy and/or you don’t really expect much rain).

The problem, of course, is that it is 100% *not* breathable so all the moisture and sweat from your body gets stuck inside the bag, runs down the sides and pools at the bottom. Not very pleasant. It also has no fastening at the top, just a huge hole. The best option is usually to sleep on top of it until it rains or you anticipate a heavy dew. Sleeping somewhere breezy and keeping the bag open will help circulate air, and lying downhill may help drain the moisture.

Summary: cheap enough that there’s no excuse not to bivouac but only a long-term option for the hardiest.

From here onwards, with one exception, you start getting quality bags and just need to choose your features and budget. British Army bivvies are the bench mark for bivi bags. They’re usually found on Amazon, Ebay or similar (try army, ex-army, british army, army surplus etc). They are big enough to fit your rucksack inside, tough enough to sleep on stones without tearing, waterproof enough for heavy rain and breathable enough to be comfortable.

All in all, they are excellent. The downsides are that they are surprisingly big and heavy (you can get one-man tents that weigh less) and, being non-hooped, just leave you to flap the Goretex hood over your face during the rain.

(N.B. “Ex-army” these days may not mean it’s ever actually been used by the army, which is fine, but just watch out for cheap imitations that are not Goretex. These will be more like the previous Hi-Gear-type bivvies described above).

Summary: big, tough, waterproof, breathable and cheap. An excellent bag. Quite big and heavy though and no hoop for the rain.

These two bags look broadly the same except for the fabric. The Storm is made from Rab’s own-brand fabric (thus cheaper) and the Alpine uses eVent (thus is twice the price).

eVent is the main rival to Goretex. Its key selling point is superior breathability. I have not used these Rab bags myself (I’ve used their other bags) but I suspect they are very similar to the Alpkit Hunka but more breathable, particularly the Alpine Bivy, and probably better quality i.e. will last longer.

Summary: good quality bivvies, more breathable than Alpkit’s Hunka but more expensive.

Rab’s Survival Zone bags are sometimes described as “sleeping bag covers” rather than bivi bags. They are very thin and are quite a tight fit around camping mat and sleeping bag. However, they are extremely lightweight and pack down very small.

The regular Survival Zone’s Pertex Shield is waterproof in all but the heaviest showers (hydrostatic head of 10,000), the Survival Zone Lite’s is not waterproof (it uses Pertex Endurance with an HH of 1,000).

I would recommend them for protecting a sleeping bag from dew, spills and other damage; for Alpine climbing where you’ll sleep on snow and want wind protection but are not worried about rain; for ultra-running or other activities where every gram counts; in addition to a tent for extra warmth in winter or so you can bivvy outside when the weather looks good.

(My wife and I used two Survival Zone Lites for 16 months’ cycling around the world. In winter we used them for warmth, year-round when camping to protect our inflatable mats and in summer to bivi outside. Read my full review here).

Summary: light enough to carry in addition to a tent and excellent for Alpine climbing or ultra-running. However, the Survival Zone Lite is not waterproof.

b. Hooped Bivi Bags

The luxury option for bivouacers is the hooped bivi: these bags have one or more poles, like a tiny tent. That means you can zip yourself inside when it rains and still sleep comfortably. They also allow better air flow meaning less stickiness and condensation inside. Pegging the bags out means they stand up on their own, stay in place and improves airflow for better moisture management. The downside is that they are not instant to pitch and strike, and they weigh a little more too.

Essentially the same design as the Terra Nova Jupiter except using eVent fabric rather than Goretex – perhaps more breathable but much the same – and having a huge hoop.

The big, square sided hoop makes getting in and out of the bag much easier than the Jupiter and allows more air in and out. It does increase the profile though so makes it a little more intrusive and may even suffer in high winds – not something bivviers usually have to worry about.

Summary: great bivi, good simple design, same as the Terra Nova Jupiter but with an extra large hoop and door.

Background

This review is based on over a decade of bivouacing across the UK and the world, from winter in the Scottish highlands, to summer on the Cornish coast, at 5,000-metres in Kyrgyzstan and roadside on Korean cycle paths, in ditches underneath dual carriageways to the summits of mountains through sunset and sunrise

Change log

UPDATED MAy 2016: Six Eight new bivvies added to the table from Alpkit, Vaude, Terra Nova, Snugpak, Highlander and Outdoor Research. Plus, hydrostatic head (HH) ratings included for all non-Goretex/eVent fabrics.

UPDATED JULY 2016: I’ve added some new software to make the table sortable by e.g price, weight and whether it’s hooped or has a mosquito net. It should also display properly on mobiles. I hope it’s helpful but let me know any problems.

UPDATED OCTOBER 2016: tables are now sortable by e.g. size/weight/price and the original source spreadsheets are now available online. Details below.

UPDATED MAY 2018: links updated. 26 bivvies now included.

Finally: is it bivi, bivy, bivvy or bivvie?

Bivouac is a real world that’s been hijacked, conjugated (e.g. bivouacing, bivouacking, bivouaced, bivouacer), abbreviated (bivvy, bivvie, bivi) and sometimes both (bivvying, bivvier, bivvied). I don’t think there’s any particular spellings that are “right”. I tend to go with bivi and bivvying but include all sorts of spellings to help people find these articles on Google. Similarly, they are sometimes referred to as bivy bags, bivy sacks, bivy tents and, simplies, bivvies.

Related posts

About the author

Tim Moss has supported over 100 expeditions across all seven continents. He has climbed new mountains, crossed a desert on foot and recently cycled 13,000 miles around the world. He is a Fellow of the Royal Geographical Society London and a Guinness World Record Holder. He aims to encourage more people to live adventurously. Read more...

Karl Ek

First of all, thank you for a very good comparison and review.
There is one Bivvy Bag that you didn’t mention. A Bivvy Bag that I believe are in the same category as Terra Nova or maybe even better.
The name is “Bivy Bag T” and are made by TAIGA of Sweden. http://www.coldskills.com/bivy-bag-t-iir-p-847-c-363.aspx

Thanks Ian. The Dutch Army Hooped Bivis look like they’ll have the same proprerties as a British Army Hoopless Bivi (i.e. tough, spacious, bulky, heavy) but with the obvious advantages of a hoop. For the prices on Ebay (~£90), they’re probably your best bet for a lower cost hooped bivy.

The US Army Modular Sleep System looks neat and is no doubt very durable. If you’re planning on using the sleeping bags as well and like the idea of an integrated system then I’m sure they’ll be good. Otherwise, my hunch is that a simpler British army bivy bag will be better (i.e. possibly smaller/lighter due to less attachments, easier to use with other sleeping bags and without a opening on the side which could leak).

Jacqui McIntosh

Trying to choose a bivvy for my husband for Christmas. He’s a ranger with the National Trust for Scotland and spends a lot of nights out on the hill. My question is do all the recommended bags have a mesh window for insect protection? Midges are hell up here!

Hi Jacqui, most bivvies do not have a mosquito net so it’s a good thing to check. Off the top of my head, I don’t know of any hoopless bivvies which have mozzie nets but the Terra Nova Jupiter and Rab Ridge Raider have them built in. They’re both excellent but expensive. You can, of course, just sleep in a cheap mosquito head net… but that might not be quite such a nice Christmas present!

Steve francis

Thanks for heads up Steve. It looks good but I think it’s a little harder to that track down over here in the UK. For whatever reason, the range of bivys in the US seems completely different from the range available here.

Jacqui, so sorry for not replying to you. I’ve only just noticed your comment. You’ve probably long since made your decision but from what I’ve read, the Highlander Hawk Bivvy is a solid choice. Proper waterproof and breathable material with a mesh face cover and good reviews. In the UK, it’s on Amazon for £50: http://www.amazon.co.uk/dp/B003BBTX8U/?tag=thenexcha0b-21

Jake

Hi,
I was considering buying a Rab storm bivi, but could find no information about the Hyperlite storm fabric used in its construction, so I phoned Rab and the helpful chap sent me an email with the details of the fabric.. I was shocked to find that it only has a HH of 3000 and to top this it is a PU coated nylon that is not I repeat NOT breathable!!! Even though the advertising says it’s breathable!

Jake

Hi ya again,
Heres the actual e-mail i got from rab concerning their Hyperlite Storm fabric as used in the Storm bivi:-

Hyperlite Storm is a proprietary fabric of Equip Outdoor Technologies LTD. It is a fully waterproof nylon thanks to the clear polyutherane coating. Hyperlite Storm is not meant to be breathable; it is meant to provide worst-case scenario weather and moisture protection.

Jake, thanks for taking the time to share that information. I was waiting for a reply from Rab. They said:

“There are two different fabrics used on the bivi. The base is made from a non-breathable fabric, which is used because of its high hydrostatic head of 10,000mmm. This is important as it is under direct pressure from your body on the ground. The upper fabric is under no pressure and so uses a lighter fabric which is breathable and has a hydrostatic head of 3000mm. This is still higher than many tent outer fabrics and more than sufficient to keep rain out.”

This obviously contradicts the email that you received but my hunch is that whoever emailed you made a mistake. All the literature suggests that the Storm Bivi is breathable and it would be a pretty poor design for it not to be. A non-breathable waterproof base, on the other hand, is common and good practice.

That said, several reviews do suggest that the breathability – regardless of the technicalities of the fabric – is poor.

Lisa Mac

Hi, the links you gave for the Terra Nova Jupiter no longer seem to sell that item? I can’t find it anywhere on the website that you link to. Mind you I’m tired right now, and it’s late, so maybe I’m missing it. Or do they no longer sell it? Regards

Hi Lisa, that’s interesting. I’ve just done a search and it seems to have almost disappeared overnight. There aren’t even any sellers on Amazon or eBay and it’s been taken off the Terra Nova website. I’ve emailed them to ask about it and will let you know when I hear back. In the meantime, Rab’s Ridgeraider is very similar.

Alistair

Hi Alistair, thanks for drawing my attention to that one. It’s not listed on the Terra Nova site so I’m not sure if it’s still being made but they’re still available online.

It’s PacLite so it will be both waterproof and have good breathability so, as you suggest, performance should be good.

Apart from it’s price (£170 for a hoopless bivy!), the most likely issues I suspect will be it’s size and toughness.

It’s only 200cm which is shorter than all of the other bivvies here and I’ve seen some reviewers who’ve sent it back because they couldn’t fit inside.

PacLite is notorious for tearing easily so it won’t be the toughest bag in the world but then the groundsheet is a different material and lightweight will always mean a compromise on durability. (Look out for new Goretex Active bivvies though – that’s a much tougher material that’s lighter than PacLite).

In summary, if you can afford it and aren’t too tall, then this should be a good quality lightweight bivy. If not, get a Rab Survival Zone or even an Alpkit Hunka.

dave woodhouse

Hi Dave, I don’t have any personal experience actually (I should probably write to them and see if they’ll give me one to test). The range in the US is very different from the range here in the UK and I’ve not yet tried to cover it.

However, they look decent to me. A good range using 3-layer Gore-Tex and Pertex Shield+ on the lighter models. Their weights are good, particularly the 500g hooped Helium Bivy. The Advanced Bivy looks very similar to the Terra Nova Jupiter which I’ve been using for over 10 years – both Goretex on top, toughened floor and single hoop (although the newer Jupiters are lighter than OR’s Advanced Bivy). It’s also interesting to see hoopless bivis with zips and mesh hoods which aren’t very common over here.

I hope that helps a little but just fire away if I can help with anything specific.

I just returned from a wet trip with my Rab Storm bivi which I used in a MLD trailstar tarp. My biggest problem was getting in and out of the thing. I use a thermorest mat inside which means the bag becomes flat and stiff. Getting in and out at the top end invites clashes with the low roof of the tarp and is almost impossible without dragging myself and the sleeping bag onto the wet ground. Not to mentioned calf cramps from the contortions to get my legs out.

Iain

Well, it looks very small, very light and very cheap. I’ve not tested it myself (although I’ve just emailed Terra Nova to ask for one) but my hunch would be that it’s either not that waterproof or, more likely, not that breathable. But if you just want something small and light to keep the dew off and protect your sleeping bag then it’ll probably be pretty good.

The lightweight alternatives are the Rab Survival Zones which are more expensive and a budget alternative would be the Alpkit Hunka.

Thanks Palle. The Bristelcine Bivi is very light but it’s only water resistant so if it rains you’ll get wet. Do you have a link for the Mountain Range one? If it’s Goretex then you can’t go too far wrong.

Thanks Tony. I’m hoping to add a comparison for US bivi bags in the near future but it’s several days’ work to put these articles together so I have to fit it around normal life and work. I’ll send you an email when it’s done though and feel free to ask any questions in the meantime.

Hi Alfie, the Snugpak Stratosphere looks most similar to the Vaude bivi on my list i.e. a decent, lower budget hooped bivi.

It’s waterproof and breathable although I think it might be using coated nylon rather than a waterproof membrane which means, like the Vaude, it might be a little sweatier and/or lose its waterproofing faster over time.

Looks like a good bag though and I’m sure it will be fine. Enjoy the Highlands!

Mike Foley

Hello Tim. Great blog and extremely informative, iv read it several times.

I want to buy a hooped bivy over here in Ireland and pickings are slim.

Im thinking about the vaude or snugpak andwas wondering would an additional snugpak bivy sack around my sleeping bag be an idea towards keeping it dry from condensation or would it be counter productive?

Should I just hold off and buy a TN Jupiter or RAB ridge raider?? Thank you and once again, tread article

Mike Foley

Hey Mike, thanks for the kind words. Were you suggesting a second bivi inside another one? I’ve not tried it but I am pretty sure that would result in a lot of sweaty condensation. Bear in mind that the condensation inside a sealed bivi bag comes from your body so it’s not a case of keeping it out but letting it out.

The best way to reduce moisture in a bivi is probably just to pitch it somewhere a bit breezy and leave it open as much as possible.

Presumably you could just pay for shipping for an online order of the Jupiter / Ridge Raider?

Mike Foley

I thought as much as regards the 2 bivys alright. The method to my madness was to put the sleeping bag inside the bivy sack to stop the moisture from your breath getting onto the bag, and to stop the sleeping bag having direct contact with the walls of the tent

Then to be in the bivy tent (because id rather be sealed up when im out) but have the vents open and a tarp over the top. I realise im adding weight and bulk but I carry a tarp and bivy sac anyway even when bringing a tent so I can leave the main pack behind and not have to worry about shelter if anything goes wrong.

I can order on line but I wanted the “rab ridge master” because of the extra hoop at the foot end and also the side door entrance simple because with the side door and a tarp over the top I have a nice work and lounge area in bad weather. Unfortunately the rab ridge master has been discontinued.

Iv read great reviews of the vaude however. If it was made of event or goretex then I wouldn’t hesitate a bit

Hey Denis, I think the Outdoor Research Advanced Bivy looks good. It’s hooped, made with Goretex, follows a simple design and is similar in both weight and price to the Terra Nova Jupiter and Rab Ridge Raider so I suspect it will be a good piece of kit. Let me know what you decide!

I’ve also been looking at Outdoor Research, and whether or not to go for the Advanced Bivi with all the features, or the Helium one which looks like a basic one but hooped. Having used both simple and fancier bivis, for more frequent use would you say it’s worth splashing out on a better bag?

I’ve only ever used the ex-army and it’s done the job perfectly fine – wonderful living outside used with a roof, no complaints. On microadventures it held up fine in snow, but I got very wet when it rained on the beach. My hoodie pillow soaked up most of the water, so it wasn’t much fun in the morning, but I was only walking 30 mins back to the car.

I much prefer sleeping out in the open that in a tent, but I want to upgrade my bivi so that it’s more comfortable if (when!) it rains, if I then need to hike the next day. I’m currently in Chile and have friends coming from the US and UK soon, so I have the option of both markets. Too much choice if you ask me!

Hey Taith, thanks for the comment. If you’re not bothered about a hoop then I don’t think there’s a big difference between the cheap (e.g. army and Alpkit) and the expensive.

I think there’s a big difference between hooped and non-hooped though. The latter are obviously simpler and easier to pitch/strike, not to mention cheaper and lighter. But a hoop is a vast improvement in the rain. Primarily keeping the rain off your face but also shedding water better by virtue of maintaining their shape and they often tend to have fully waterproof floors.

Personally, I have a hooped bivvy so almost always use it and find it much nicer. Some would baulk at the cost (including me now!) or just prefer the simplicity of non-hooped.

Outdoor Research contacted me recently so I’ll hopefully be able to review the Helium Bivi. 500 grams and hooped!

Fabio.

Brilliant article Tim! I am considering a divvy and so far the sort list is the Highlander Hawk Bivvy, an american army bivy or a belgian army divvy (of course I am also thinking of the good old British bivvy . . . But I do want a mesh and I am on a budget. Any advice or notes, especially concerning the Highlander Hawk Bivvy and american body (to be used with my own sleeping bag) will be much appreciated. The hills are calling!

Hi Fabio. You will never go wrong with an ex-army bivi. They’re often a bit big and heavy but always do a great job.

But if you’re keen for mesh (and don’t want to sleep in a mosquito head net) then the Highlander Hawk Bivi looks good to me. Proper waterproof/breathable material, built in mosquito mesh and good reviews. It’s heavy for hoopless (over 900g) but then so are army bivvies. In the UK, the Highlander Hawk’s selling for less than £50 too which is good value.

Fabio.

Many thanks for the advice Tim! I decided at the end to go for the ex-army bivvy: As you say, they seem to tick lots of boxes and are very affordable. Test it/use its few time to see if the mesh thing was something more in my mind that in reality (besides, slug cannot be that bad . . . can they?) an allnighter and take it from there. There is always a fall back position.

Dan P

Hello! Im looking for a lightweight, small pack size, and breathable bivvy that wont break the bank. I was hoping that the kne im considering was in your table but its not! Any thoughts on the Snugpak special forces bivi?

Hey Dan, thanks for flagging up the Snugpak Special Forces Bivvi. Looks like I need to add that to the list.

What stands out from its stats is the hydrostatic head of 5,000mm (see Bivvy Bag Buyer’s Guide above for an explanation). That means it will probably be fine in a short shower but won’t keep you dry in heavy rain or if you lie on wet ground.

At 440g, it actually looks slightly heavier than the Alpkit Hunka which is cheaper and has a higher hydrostatic head (10,000mm) so that might be a better option for you. Back in stock this month, apparently.

Chris

Such a useful review on a complicated subject. I was also looking at the Snugpak Special Forces bivi. Their website claims 340g for the regular and 400g for the extra-long, which is not significantly heavier than the equivalent Alpkit Hunka, and lighter for the XL.

Also the Snugpak SF seems to be wide enough to fit a sleeping mat inside the regular if you check some of the YouTube reviews, which the Alpkit cannot unless you buy the XL. I haven’t managed to try this yet though so some mats may not quite fit.

Finally it has a zip which helps with getting in and out, which the Alpkits do not.

You are right about the waterproof rating though, which is 5000mm vs the Hunka’s 10000mm, although I do intend to use it with a tarp. It is also more expensive than the Hunka, although you can find them online for around £66 for the regular vs the Alpkit’s £48.

There is also a Snugpak (non-SF) Bivi which is bascally the same but lighter as it doesn’t have the zip.

Excellent review. My own bag is a WildCountry bag about 8 years old now. I can’t find any similar on the www, but it’s outstanding features are that as well as being sturdy and very breathable, the head end has a plastic window which can be held off the face either by a monopole and guy cord, or by suspending the head end from an overhead branch, fencepost etc, using a bit of paracord atatched to the purpose made loop on the bag. You get the same effect as a hooped bivvi but obviously you need to have something to tie it to! Other pluses are that is is big enough to put your sleep mat inside and that there are small peg loops at each corner if you wish to pin your bivvy down – it’s a good idea in this one as the floor panel is a nonbreathable material, and the upper is a nice olive green goretex material. Keeps your goretex bit clean and unworn if you roll over inside the bivvy. It’s kept me dry in Cumbrian monsoons – I still proof it and use it. The only downside – weight and pack size… my Karrimor one man tent isn’t much heavier.

I’ve used a HiGear bag once or twice – it’s just as you describe Tim.

Finally – just landed an Alpkit Hunka XL in sexy kelp….. it’s coming down in stair rods tonight. Maybe time for a field test!

Francis

Dear Tim, many thanks for an excellent article. For a light weight cycle your across the Alps I am planning to bivvy. I am deciding between rab alpine (more expensive but lighter), or the highlander hawk (cheaper, heavier, but sturdy, low profile). Given pros and cons, which would you go for? Thanks again.

Hi Francis, good question. I think it just comes down to cost vs weight. The Rab Alpine will be the better bag at just over half the weight but it’s almost four times the price. If you’re feeling flush and going really lightweight (e.g. no panniers) then go Rab. If you’d rather save pennies or are using panniers then go Highlander.

Of course, you could get the Alpkit Hunka which is both cheap and light!

Robin.

Good article Tim. I often use a rab ascent bivi (similar to the rab storm but made of event). It’s quite a clever design in that it has a zip out bug mesh and a cord attached to the top flap That can be supported by a walking pole to hold the mouth of the bivi open. The bug mesh keeps the mozzies out but you get plenty of fresh air circulation.
I also have a ridge raider. One thing that I think would be worthy of considering in your article is whether each bivi leaves room for a sleeping bag to loft if an air matress is used.
I had a very cold night in my raider last winter because I used an exped synmat 9 UL in my bivi. I was sleeping in a rap ascent 900 bag but unfortunately the mat compressed most of the loft out of it. I was so cold my muscles cramped up and painfull. The storm was too fierce to risk moving as visability was only a few feet. (Pen y fan) I have since bought a thermarest Xtherm which is not as thick. Yet to try it in winter.

Rob

Thanks for that Tim. I live in the Alps and I’ve recently started taking my 7 year old son out hiking with overnight bivis and he absolutely loves it. After spending a very shivery night under the stars in october I thought it was about time we invested in some bivi bags and this page has given me all the info I need!

Tim H.

Thanks for all the great research and information. I need a bivi for a 6 month motorcycle trip through Central and South America. I plan to stay in cheap hotels each night. The bivi will be for emergencies only when I get stranded or can’t find a hotel. I hope to never use it. But if I must use it, it must be waterproof and hooped. It must protect me from getting soaked by a heavy rainstorm.

I understand as you stated that waterproof and cheap materials (non-gortex) means lots of interior condensation. So here is my question: In an all night rainstorm, 100% humidity outside the bivi, will it be any less humid inside the best gortex bivi versus the cheap AquaQuest “Hoopla” bivi in those conditions? My understanding of porous membranes says no, it will not be any better. Am I wrong on this? I think the expensive gortex will only help inside dampness if the humidity outside the bivy is lower than the humidity inside the bivy. Trying to figure out if the cheap hooped bivi that I hope to never use is the better buy for my application than the expensive gortex hooped (terra nova jupiter or rab ridge) bivi.

Thanks for the comment Tim and an interesting question. I’m not sure I paid enough attention in school to be able to answer it with science. However, even if you’re right about those nights that are 100% humidity and raining all night, what about all the nights that aren’t?

Either way, I love your thinking and would really like to hear how you get on.

For what it’s worth, if you’re really expecting long, wet nights then a tent is probably the only real way to stay dry. You can get some that way less than a hooped bivvy.

Tim H.

I looked into this a little deeper and if anyone is interested, here are my findings in simplified terms. Apologies in advance for the length of this. If you completely under the physics of partial pressures and equilibrium and the structure of gortex and why it works, skip to the last paragraph for the “nugget” in this whole thing.

Gortex material is a very fine grid or filter or screen. Each fiber in the grid is plastic that does not absorb water. The space between these gortex fibers that are woven together like a screen on your window, are open. The opening is large enough to allow gas to pass through the screen but not solids or liquids. A water molecule in its gaseous state (water vapor) is thousands of times smaller than a water molecule in it’s liquid state. So water vapor can move through Gortex in either direction but liquid water molecules are too big and will not pass through the open areas of the grid or screen in Gortex, so it will stay on whichever side of the Gortex it is on.

So the gortex is a porous membrane with a grid or screen size large enough to allow water vapor, a gas to pass through but small enough to prevent liquid to pass through. The laws of physics prove that nature wants to equalize the environment on each side of that porous membrane, the gortex. If there are 100 “pieces” of water vapor on one side of the gortex and 80 “pieces” of water vapor on the other side of the gortex, the side with the 20 extra pieces acts like it is of higher pressure and wants to equalize with the other side so both end up with 90 “pieces” of water vapor. The side with 100 pieces and thus more pressure pushes 10 pieces out to the other side and then the pressure on both sides is equal so they no longer change. The pressure difference in this example is small so the rate at which the equalization occurs is slow. If it was 100 pieces of water vapor on one side and 15 pieces of water vapor on the other side, the difference is much larger and thus so is the pressure and then so is the rate or speed of change to the equalization state.

When you create water vapor in your tent/bivi through perspiration (sweating) and respiration (breathing) and evaporation (your wet jacket and boots you brought in with you) you build up a certain number of “pieces” and “pressure” of water vapor on your side of the gortex porous membrane (inside the tent/bivi). If there are more “pieces and pressure” of water vapor on the other side of that gortex (outside the tent/bivy), it will try to equalize, bringing more water vapor into the tent/bivi until it is equal on each side of the gortex or in other words, the same humidity inside the tent/bivi as outside. And of course the opposite holds true, if it’s more humid inside the tent than outside, nature will cause the conditions to equalize, reducing the humidity inside the tent until it is equal to the humidity outside the tent. The rate or speed of that change occurring is dependent on the magnitude of the difference in the pressure on each side, which equates to the percentage or number of “pieces” of water vapor on one side compared to the other.

So what does all of this mean. Gortex works well and relatively quickly shedding your water vapor to the outside of your tent or jacket when there is a big difference between the humidity (water vapor) inside your tent/jacket versus outside your tent jacket. As the outside weather gets more and more humid and approaches the humidity inside your gortex tent/jacket, the shedding effect of humidity slows down and eventually stops when humidity is the same inside your jacket as outside your jacket. And, it can even reverse, pushing humidity from the outside air through the gortex to the air inside your jacket/tent if the water vapor (humidity) outside is greater than the humidity inside your tent/jacket.

So the nugget I found in my research that pertains to my original question is this. The humidity outside is seldom 100% at ground level when you are getting rained on. The humidity is 100% where that water vapor is turning into water (in the cloud) and then falling to the ground where you are but that may be happening 1000’s of feet above you and your tent. If you are in mist or fog, then the outside humidity is at or close to 100% and you will also be at 100% humidity inside your gortex jacket or tent very soon. But during a rainfall, the air outside of your tent could be at 65% humidity, still pretty comfortable compared to 80%-90% humidity inside a non-breathable tent/bivi. The gortex tent/bivi won’t exceed the outside humidity. See below a website address that explains this pretty well if I did not. http://andrewskurka.com/2012/breathability-its-importance-mechanisms-and-limitations/

Freya

Magnificent article, thanks! Which one do you think is more breathable: the Alpkit Hunka or the Highlander Hawk? Both are made of nylon, but the Alpkit is more water resistant (and cheaper) and thus might be less breathable. I’m thinking of fixing a mesh net in the Alpkit, so I would basically get a cheaper, lighter and more water resistant version of the Hawk – or at least that’s the idea.

I’ve not used the Hawk yet I’m afraid but the Alpkit one is good and the breathability is fine. Alpkit stuff is always decent – not the best but reliable – so that would be the safer bet. The hydrostatic head of 4,000 on the Hawk won’t be good enough in heavy rain.

P.S. Sewing on a mesh net sounds great. If it’s too fiddly though, a mosquito headnet would be a crude alternative.

I like the Army Gortex Bivy Cover; the side zipper is very convenient, and it is nicely breathable. However, I also have the RAB Bivy (the model is yellow on top and black floor. I think the floor is nylon and the yellow top is event. The floor is the problem — I have never had an experience with it that gave me a dry night — the condensation (I believe caused by the nylon floor) spoils the whole experience.

Sherpa

Very interesting list, thanks for the effort! A few additional, lightweight contenders (I hope I didnt overlook anything in your list): Terra Nova Moonlite; Montbell Breeze Dry Tec UL Bivy; SOL Escape Bivi; SOL Escape Lite Bivi. If you have any insights on these, they would be very much appreciated.

Terra Nova Moonlite – I’ve seen this before but it’s currently out of stock so I’ve emailed Terra Nova to see if it’s coming back. It’s really light for a waterproof/breathable bag so I’d be interested to try it. If it’s still being made then I’ll add it to the chart.

Montbell Breeze Dry Tec UL – seems to be an American bag that’s not stocked in the UK. I’ve not included US bivvies here because their range is, for the most part, completely different. Perhaps I should do a separate article for them.

SOL Escape Bivis – these look really interesting as cheap, lightweight bags. The reviews on them look alright so I’ll see if I can get my hands on one. They also look like US products but seem to be available here in the UK too so I’ll get them on the table next time I update it.

Jas Holden

I wonder if you have heard of a new waterproof and breathable fabric called Hipora or Hypora that is coming from Korea? Several top brands of gloves for skiing and motorcycling have this. I recently bought a bivi bag with this Hipora from a Korean dealer on Ebay America for $35. I have not had a chance to give the bag a good test since I sweat very little and have never had condensation in the US Army goretex bivi. This is the first use I have heard of for Hipora other than gloves.

Somewhere on Youtube there is a video of a man wearing the gloves and putting his hands into a bowl of water and staying dry, and then pouring hot water into the gloves and having a cloud of steam form around the fingertips.

Zac Caldwell

Hi Tim,
I’m going on the Fjallraven Classic hike in Sweden and only 15 years old. I’m looking for a bivy bag that can withstand the conditions of Sweden in August as well as being very small and compact. I have done some research and most of the products out on the market look great but reviews on most say otherwise. Most of the issues are condensation or not waterproof and too stuffy from being too small. The Outdoor Research bivy bags look very good but the Helium had little structure and looks like could rip of and rough objects hit the surface. The Advanced bivi of theirs looks amazing and everything I’m looking for but way out of my budget around £100-180. Do you have any recommendations? Any help would be greatly appreciated. Thanks again,

Tobias Christensen

Hey Tim!
Thanks for the great comparisons.
What bivy would you recommend for unsupported bikepacking races? It needs to be waterproof, breathable and light.. Seems impossible..
I will sleep under the open sky every night, so waterproofness is a must :)
Thanks again.

Hey Tobias, I’d either go for the Rab Survival Zone (not the ‘Lite’ version) Terra Nova Discovery LITE. I’ve not slept in either myself but the former has been around for a long time and the latter’s made with Goretex so waterproofing is guaranteed.

Alternatively, I’d consider that little bit extra weight for a Outdoor Research Helium Bivy. Only 500g but it’s hooped which is so much better in the rain.

Eddy

Tim…. I know this is a long thread going over a number of years , a lot of knowledge displayed…… I have been looking for a twin hooped ex-army bivy that is shown on you tube …. supposed to be an ex SAS sniper set up ( handy for hunting) , they don’t seem to be available anymore … (A) any idea where I might locate one (B) there is a ex-Russian military set up advertised however it seems not to be breathable in the absence of the British army what do you reckon about the Russian ex-military observation twin hooped bivies ……Carinthian do a similar set up however they are Wayyyyyy over my budget.
For your help thanks .
Eddy

A) My only suggestions would be the obvious online searches (Ebay, Amazon, Google, Google Shopping and perhaps Gumtree) and trying local army surplus stores.

B) I’ve never seen a Russian military bivvy and I can’t find any online to look at. If it’s really not breathable then avoid it as it’ll be rubbish. Better to get a proper double-hooped bivvy (like the incredibly expensive Terra Nova Saturn) or settle for a single hoop (like the Snugpak Stratosphere or Helium Bivvy if price is the issue)

Jakub Čejka

“Super Light Cover” by the Czech company HighPoint (formerly Schwarzkopf) should definitely be added here! I just discovered it now and am buying it – so cannot review yet.
It weighs around 230g and claims a 20t waterproofness and 25t breathability (Writing from memory, maybe I am messing up the numbers from the heavier “Dry Cover” by the same company). I just suggest you check it out for yourself

Daniel Bardsley

Hello Tim
This is an excellent page. Another bivvy that you might want to consider including is the Karrimor X-lite. I have one of these and on the several times I have used it there has been very little or no condensation. It looks almost identical to the Alpkit Hunka and the breathability statistics given by the manufacturers are the same, but it’s cheaper and more easily available.
Thanks.
Daniel

Fraser

Tim just in to assist in your hunt for info / specs on the Karrimor X-Lite Bivi, there is a french site with some info on what appears to be the same product, I think it’s had a face lift but it’s the same. If you go to this page and use google translate – https://www.randonner-leger.org/forum/viewtopic.php?id=24635 it lists the approx dimensions as Overall Length: 215cm (+/-) Shoulder width: 75cm (+/-) Width feet: 50cm (+/-). I’m going to order one as it seems quite a view have tested it and it appears to be a decent bit of kit, was a toss up between that and an British Military Bivi, but I think the low weight / bulk will be worth it.

Simon Clark

Brilliant Info Tim, thanks.
For feedback, I used an OR hooped helium bivy for 130 nights in a year running around the coast of Britain and stayed dry in all weathers, with varying condensation, throughout the year. The significant factor is my sleeping bag, though often wet on the outside,was never so inside. I love it.
Question: I want to buy a discretely coloured double, lightweight bivy for two of us, not bright orange, any leads?

My only other suggestions would be to get one custom made from a large sheet of Goretex or combining two singles. I will let you know if I come across any others and do come back if you find one yourself.

I find the solar bag works way warmer inside a sleeping bag rather than outside. Regular bivy works way better in survival situation than light. The name of game is holding in the heat of your body and u spend most of your time trying to keep the bag snug around neck and is pain. I wish they made the hoodie version with draw string in the no zipper version like the lite. Too much heat loss with zipper.﻿

I bought The Rab Ridge Raider bivy sack. The upper part of the bivy sack is made of a 3-layer 40-denier eVent fabric which is known for its superb breathability and durability while the floor is made of durable abrasion-resistant nylon. The bivy sack comes with one DAC Pressfit pole so that you can suspend the material in the head area. When the head area is suspended the bivy sack offers an internal height of 58 centimeters which is indeed impressive for such a light and small (when packed) shelter. The pole comes in the external sleeve and can be secured with stakes to stay upright. Additionally the bivy sack is equipped with six stake loops and a no-see-um mesh door to keep the insects out. All in all, the Rab Ridge Raider bivy sack is a great option for lightweight hikers and mountaineers who want a shelter that is bigger than an ordinary bivy sack, but smaller and lighter than a one-person tent.

Aaron

Hey Tim!
Thanks a lot to share your impressing experiences in such a widespread comparison!

I’m in the market for a few weeks, researching a bivy bag to buy. Actually I’m comparing the RAB ridge raider with the TN Jupiter lite (yes, after some research I found one seller still having a few in stock). My major question right now is about the materials. There is a lot written about gore tex vs eVent but nothing about the “TN Moonlite fabric” used in the last iteration of the Jupiter bivy, wich appears to be the lightest breathable and waterproof hooped bivy on the market (only 680g including pole and pecs!). Do you have any experiences with the Jupiter lite and can you tell something about brathability and durability of the “TN Moonlite fabric”?

Aaron

Thanks for your answer. Scanning the web for experiences with the Helium bivy made me worry that it does not perform very well in severe weather. Testers reported that they had water breaking through the membrane when rain got heavier than drizzle.
For me it’s pretty important to have a safe shelter even in thunderstorms because I had a lot of them on my last trip. But your commend made more clear to me that the combination of comfort, durability and safety from weather is indeed a factor of weight. It seems that all of them in combination produce products heavier than 700g.

Those Helium experiences sound about right. After a night of heavy rain the foot of my sleeping bag was damp from a puddle that had formed, while my friends in (Goretex) Jupiters were fine. It’s an excellent bivvy for the price and weight but not as waterproof as a Goretex one. Good luck!

I live in the UK and want to start taking my kids camping under the stars. The biggest threat we will face in our first year is dew. Does it matter what sack you get at this point please? Thanks for your sharing so much..

Dew is definitely an issue, but I don’t think the type of bag will matter too much.

For example, if it really is just due that you want to deal with (and not rain) then even the “water resistant” bags will do the job (e.g. Rab Survival Zone Lite or Vaude Biwak I). They’ll probably be nicer to sleep in too because even the most breathable waterproof materials (e.g. eVent or Goretex) are still pretty sweaty.

The only thing I can think of that that might reduce dew (besides a light breeze and camping on top of a hill) is having a hooped bivvy that’s pitched tautly. But it’s probably not worth the extra cost/hassle just for that.

To be clear, there is a difference between drew on the outside of the bag and condensation on the inside. The type of bag will certainly make a difference to the condensation inside, and I’ve commented on that in the article above (anything about breathability will influence the amount of condensation).

Chris

If you are in the UK I can recommend the Alpkit Hunka bag. I used one for 13 nights last year and it kept me dry both from dew and condensation. I also got rained on one night (under trees) and that was fine too, but Alpkit do some tarps too if you want extra protection.